| What does it mean to be alive? How does thinking work? Is my reality different than yours? If your mind has ever wandered across this existential terrain, you've joined the ranks of countless philosophers, scientists and everyday people who have, for thousands of years and likely more, probed their own consciousness.
Despite all that attention, the phenomenon of consciousness continues to slip through our grasp. We try to define it, find it, even create it — and we can't. Consciousness is to neuroscientists and philosophers as dark matter is to physicists: It's here and there, but nowhere tangible. Our understanding remains just out of reach.
This is not for lack of trying. Today there are dozens of competing theories on consciousness — what it is, how it arises and how far it extends. The only thing that all theories can agree upon is that consciousness is some kind of subjective inner experience.
So how can scientists test for something that's so personal? "There's lots of disagreement," said Claudia Passos-Ferreira, a bioethicist at New York University who recently organized a conference on infant consciousness, which I attended. One way in is to debate who (or what) has consciousness. At the end of the meeting, Passos-Ferreira shared the results of a survey she had distributed to the attendees, who were mostly neuroscientists, philosophers and psychologists, to probe their conceptions of what kinds of beings have consciousness.
All of the 87 survey participants agreed that adult humans are conscious; 93% said cats, and 72% added fish. Around 80% believed that human babies are conscious at birth, and the majority thought that consciousness arises around or after 24 weeks (roughly six months) of gestation. As the survey moved away from vertebrates, the numbers dropped: 42% for flies, 33% for worms and 15% for plants.
Some even believed that nonliving objects are conscious: Two people said particles are conscious, six said current AI systems are conscious, and 32 said future AI systems will be conscious.
The question of consciousness is no longer just about understanding a phenomenon of our existence; it's also about the effects of possible innovation. Whether or not we understand it, can we create it?
What's New and Noteworthy
In 2023, two popular theories of consciousness faced off at the 26th meeting of the Association for the Scientific Study of Consciousness in New York City. One, the global neuronal workspace theory, holds that consciousness is about "thinking" and stems from the front of the brain. In this case, information about the world flows into a conscious "workspace" that the brain can use to make decisions and learn. The other, integrated information theory, says that consciousness arises from sensory areas in the back of the brain. It maintains that conscious experiences are integrated — processed as complete scenes rather than divided into small parts. The jury's still out on which theory is correct: Researchers conducted experiments to test both theories, and they could not crown a champion.
How does the brain build consciousness from physical material? A few decades ago, the philosopher David Chalmers called this the "hard problem" of consciousness. But according to Anil Seth, a neuroscientist at the University of Sussex, Chalmers was being pessimistic: We are slowly but steadily making progress on understanding how consciousness arises, he said, even if it seems impossible to explain with physics, chemistry and biology. "If we stop treating consciousness as one big scary mystery in search of one big eureka moment of a solution, and follow the same strategy that biologists followed when understanding life, the hard problem of consciousness may dissolve," Seth told Quanta's video producers.
But enough about us: What about animals? In 2024, scientists and philosophers presented a declaration arguing that consciousness may extend beyond humans and our relatives, such as great apes, and may also be experienced by animals very unlike us. According to the document, accumulating evidence suggests that all vertebrates and many invertebrates, such as cephalopod mollusks, decapod crustaceans and insects, may display "phenomenal consciousness," meaning that it is "like something" to be that creature. Bumblebees, for example, push and rotate small wooden balls for no other reason than, it seems, play. Octopuses are thought to feel pain, and crayfish may experience states that resemble anxiety. All of these species have brain structures that are extremely unlike our own, but that doesn't disqualify them from conscious experience.
As people have been doing for thousands of years, experts and nonexperts alike will undoubtedly continue to debate the boundaries, requirements and definitions of consciousness. Whether or not we ever figure it out, it's hard to imagine that we'll ever get tired of trying. |
